1. Field of the Invention
The present invention relates to a brain function examination by the utilization of a pupillary light reflex, eye movement, neuro-psychological test and behavior evaluation. More specifically, the present invention relates to a brain function examining apparatus and a method therefore, wherein indexes such as the pupillary light reflex and eye movements exhibited by a subject is detected to determine a brain disorder such as, for example, the degree of senescence of the brain, disorder of the autonomic nervous system, the dementia, Meniere disease, vertigo or the like.
2. Description of the Prior Art
It is generally said that the size of a pupil decreases with age (for example, Ishikawa, et al., xe2x80x9cFukyuu-gata Denshi Doukoukei Irisukohda (C-2514) (Neuro Ophthalmology), Vol. 10, No.2, pp. 106-110, 1993). The smooth muscle that adjusts the size of the pupil is governed by the autonomic nervous system and the size of the pupil and/or the pupillary change reflect the degree of activity of the autonomic nervous system.
It is also pointed out that the pupil is associated with the Alzheimer""s disease which is generally considered closely associated with the brain function. L. F. M. Scinto, et al. have reported that by measuring the rate of dilation of the pupil before and after a dilating agent is instillated, diagnosis of the Alzheimer""s disease which is considered one of dementia is possible (xe2x80x9cA Potential Noninvasive Neurobiological Test for Alzheimer""s Diseasexe2x80x9d, Science, 266, pp. 1051-1054, 1994). According to this method (hereinafter referred to as an instillation method), since diagnosis of the Alzheimer""s disease is done in reference to the rate of dilation of the pupil, the result of such diagnosis is subjective. In this respect, it may be said that the instillation method is more excellent than the interview-based medical examination which tends to result in subjective results. Determination based on the interview-based medical examination includes, for example, The Revised version of Hasegawa Dementia Scale (HDSR) which has hitherto been used in diagnosing dementia. It is noted that measurement of the pupil based on the installation method requires 30 minutes and cannot be applied to some of subjects suffering from ophthalmic diseases. Furthermore, reliability of the eye drop test is controversial recently.
To overcome the above discussed inconveniences, a diagnosis technique is available in which the characteristic of the pupil (the pupillary light reflex) is measured to determine if dementia is apparent. This is based on researcher""s report that the normal and dementia cases exhibit different pupillary light reflexes (Shi, et al., xe2x80x9cA Study for Objective Measurement of the Senile Dementia by Light-Reflexxe2x80x9d, Iyou Densi to Seitai Kougaku (Medical Electronics and Bio-engineering), Vol. 36, No. 3, pp. 210-214, 1998). According to this diagnosing method, unlike the installation method, measurement of the pupillary light reflex completes in a short time and has an advantage that the measurement brings no side-effect.
However, according to the Shi, et al. report, the normal and dementia cases are merely compared with each other by calculating predetermined indexes (pupillary constricting rate, pupillary constricting time and pupillary redilating rate) indicative of the pupillary light reflex. Accordingly, it is not possible to output (display), for example, a subject index and an average index for the dementia cases and then to utilize a relative relationship displayed in determining if the subject is suffering from dementia or the like. Also, since the pupillary light reflex varies from person to person as is the case with physiological indexes, it cannot be said that with only the three indexes reported by Shi, et al. the manner of pupillary change is sufficiently grasped. Accordingly, determination of the dementia, the degree of autonomic activity, the degree of senescence of the brain function or the like with the use of such small indexes lacks reliability.
Furthermore, even if a large number of the indexes representative of the pupillary lights reflex are used, there are cases in which deviation is generated in the results due to individual differences. More generally, using only one type of physiological index may generate deviations in the results due to individual differences. With this, it is unable to meet the requirements of the persons concerned for further improving the reliability of determination.
It is an object of the present invention to examine brain functions at higher accuracy by combining various independent indexes (pupillary light reflex index for reflecting the degree of activity of the autonomic nervous system, visual system functional index concerning oculogyration for reflecting the degree of activity of visual cortex of brain, intelligence evaluating index that reflects the intelligence test of the subject, behavior evaluating index concerning the behavior of the subject, etc.).
It is another object of the present invention to put together the information on various independent indexes, convert them into another values with fewer indexes, and to examine brain functions more easily by using the converted values.
To achieve these objects, an apparatus which examines brain functions of a subject comprises two or more examining units, which are a pupillary change examining unit which examines characteristics of a pupil of the subject and which calculates a pupillary index, a visual system function examining unit which examines visual system functions of the subject and which calculates a visual index, an intelligence examining unit which carries out an intelligence test on the subject and which calculates an intelligence evaluating index, and a behavior examining unit which provides a behavior evaluating index that shows a result of behavior test of the subject. The apparatus further comprises a memory device which stores a plurality of indexes presented by the two or more examining units, and an output unit which outputs the plurality of indexes stored in the storage unit. The output unit sends data representing a plurality of indexes to, for example, a display and/or a printer.
The brain function examining apparatus according to the present invention further comprises a multivariate calculator which calculates at least one discriminant score in the quantity less than a number of input values based on a plurality of input values. The multivariate calculator calculates the at least one discriminant score using the plurality of indexes presented by the two or more examining units and the plurality of reference indexes accumulated in the database as the plurality of input values for calculating the at least one discriminant score.
According to the present application, it is possible to achieve the accurate determination of dementia, and further achieve the determination of degree of senescence of the brain function.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.